Thursday, April 01, 2010

Vitamin D Supplementation: The Jury Is Not In

"Despite the promise for disease prevention suggested by available studies, we believe that the evidence for widespread use of high-dose vitamin D supplementation in the general population remains insufficient."- Vitamin D Supplementation in the Age of Lost Innocence, Annals of Internal Medicine, March 2010

And from a recent article in the New York Times:

"Since most of the data on vitamin D comes from observational research, it may be that high doses of the nutrient don’t really make people healthier, but that healthy people simply do the sorts of things that happen to raise vitamin D.

“Correlation does not necessarily mean a cause-and-effect relationship,” said Dr. JoAnn E. Manson, a Harvard professor who is chief of preventive medicine at Brigham and Women’s Hospital in Boston.

Despite the promise of vitamin D in observational studies, research into other supplements shows it’s difficult to document a benefit in otherwise healthy people, and virtually impossible to predict potential harms, notes Dr. Eric A. Klein, chairman of the Glickman Urological and Kidney Institute at the Cleveland Clinic."- The Miracle of Vitamin D: Sound Science, or Hype?, New York Times, Feb 2010

It's nice to see more thoughtful reporting on this topic, especially as the vitamin D industry gears up to rake it in:

"According to the lab company Quest Diagnostics, orders for vitamin D tests surged more than 50 percent in the fourth quarter of 2009, up from the same quarter a year earlier. And in 2008, consumers bought $235 million worth of vitamin D supplements, up from $40 million in 2001."- The Miracle of Vitamin D: Sound Science, or Hype?, New York Times, Feb 2010

Vitamin D supplements raise levels of 25(OH)D in the blood; this is not the active form of the vitamin. Do higher blood levels of a precursor reduce incidence of disease? This causal relationship has not been determined.

2 comments:

Interesting article, the comments to the referenced Annals of Internal Medicine article were particularly good.

With Vitamin D one should never forget that it is misnamed as a Vitamin, it is actually a pre-hormone and not something normally obtained through diet; under normal conditions our bodies synthesize it in our skin from Cholesterol when exposed to Ultra Violet light in the UVB wavelengths.

Avoiding the sun, low sun angles during winter in northern or southern latitudes, wearing sunscreen, and having dark skin or a tan all limit the supply out bodies can produce. One way of thinking about it is similar to Chlorophyll in plants, a photochemically induced biological process. The effects of this process are varied and widespread throughout the body.

While increased supplementation is being proposed, it's effectiveness is still debatable, a much better solution is small amounts of sun where possible, or extremely modest exposure in a tanning bed; five to ten minutes, two or three times a month. A review of current research by Dr. William Grant, indicates that these methods alone could prevent 400,000 premature deaths annually in the US, and extend life expectancy by two years.

There really is no legitimate correlation between current Vitamin D research and previous studies on other true Vitamins like Vitamin A or E which are nutrients supplied by food, and have a much more narrow effect on the body.

It is a shame that competing commercial interests will muddy the water on this issue just like every other issue in modern life.